Meeting Abstract
Previous studies in a variety of vertebrates indicate that stressed animals exhibit an acute increase in circulating plasma glucocorticoid levels and a consequent immunocompetence modulation. Little is known about physiological reactions to stressors in Amphibia and the consequences of elevated glucocorticoids on the animals’ immune response. In order to further explore the relationship between glucocorticoids and immunocompetence, we subjected newly captured toads to a restraint challenge with or without movement restriction (maintenance in a small plastic bag vs. maintenance in a bin) for 24h. Our goal was to test if both types of restraint can be considered a stressor, promoting elevated plasma levels of corticosterone (CORT) and reduced immunocompetence in the invasive cane toad species, Rhinella marina, from Florida/USA. We predicted animals subjected to restraint with movement restriction would exhibit higher levels of CORT and immunosuppression. We analyzed CORT, neutrophil/lymphocyte ratio (N:L) and bacterial killing ability (BKA). CORT significantly increased 8 fold (t = -3.69; p= 0.01) in response to restraint without movement restriction, while animals who were movement restricted only exhibited a non-significant 3 fold increase (p=0.29). Additionally, restraint with and without movement restriction increased N:L 2 fold, but had no effect on BKA. It may be the significant CORT increase in animals that could move more is related to CORT associated metabolic effects. We also found a significant, positive correlation between BKA and N:L (r = 0.725; p = 0.04) after restraint without movement restriction, which may be related to increased mobilization of neutrophils into the blood stream.
